JP5220340B2 - COMMUNICATION DEVICE, COMMUNICATION SYSTEM, COMMUNICATION CONTROL METHOD, AND COMMUNICATION CONTROL PROGRAM - Google Patents

Description

  The present invention relates to a communication device, a communication system, a communication control method, and a communication control program that perform multi-hop data transfer, and in particular, can perform forward error correction (FEC) with appropriate redundancy. The present invention relates to a communication device, a communication system, a communication control method, and a communication control program.

  A wireless multi-hop network is a technology that allows data to be transferred in multiple hops without installing a wired communication infrastructure, enabling wide-area communication, and has attracted attention from the viewpoint of network autonomy and mobility of communication terminals. Technology.

  Among them, it is proposed that multicast communication in which data is transferred from a single transmission terminal to a plurality of reception terminals on a wireless multi-hop network is applied to services such as information distribution.

  When multicast communication is performed on a wireless multihop network, broadcast communication is used in the wireless communication section.

  However, on wireless multi-hop networks, packet loss may occur due to the “hidden terminal problem” unique to wireless multi-hop networks, in addition to packet loss that occurs due to radio wave fluctuations and fading that occur in wireless communications. become.

  These factors vary greatly depending on time, place, and network configuration, and are characterized by large fluctuations due to changes in radio wave conditions and movement of communication terminals. Further, the packet loss caused by these factors cannot be recovered by broadcast communication without retransmission.

  Note that the above-mentioned “hidden terminal problem” means that when communication terminals located at a distance where they cannot sense each other perform data transmission at the same time, radio interference occurs at the communication terminal at a position where both data can be received. The problem is that data cannot be received.

  On the other hand, application-level multicast communication is often used for streaming.

  In streaming, packets that arrive after the time to be played are not used for playback. Further, instead of allowing a certain amount of packet loss in communication, importance is attached to low delay.

  For this reason, in streaming, as a method for recovering packet loss, automatic retransmission control that requires retransmission of lost packets: redundant data is added to packets in advance with more appropriate redundancy than the ARQ (Auto Repeat reQuest) method. Forward error correction: FEC (Forward Error Correction) method is applied to recover lost packets.

  Note that with the FEC method, the higher the redundancy, the more information is added to the packet, and the probability of occurrence of delay and packet loss in the communication path increases, so it is important to set an appropriate redundancy. Become.

  Furthermore, when the content of multicast streaming is a moving image, frames (still images that are units constituting a moving image) coded by a moving image coding method such as MPEG2, MPEG4, H.263, and H.264 are transmitted as data. The

  When this frame exceeds the maximum size of a packet flowing through the network, it is divided into a plurality of packets for transmission.

  Note that the I-frame (Intra-coded Frame) of the video has a larger data size than other frames (P-frame: Predicted Frame, B-frame: Bi-directional Predicted Frame). Often to do. For this reason, a plurality of packets are continuously transmitted in a short time, and burst traffic is generated.

  When burst traffic occurs on the wireless multi-hop network, burst traffic occurs in the entire wireless multi-hop network, and the probability of occurrence of packet loss due to the “hidden terminal problem” increases. In addition, if the I frame is lost, the quality degradation at the time of moving image reproduction becomes large.

  For this reason, in a wireless multi-hop network in which packet loss frequently occurs, it is important to take measures against I frame loss in order to reproduce high-quality moving images.

  An I frame is a frame that includes all information of one frame of a moving image. For this reason, it is possible to restore one frame using only the I frame.

  The P frame is difference information between the corresponding frame and the previous I frame or P frame.

  The B frame is difference information between a corresponding frame and an I frame or a P frame before and after the corresponding frame.

  In addition, as a technical literature filed prior to the present invention, there is a literature that discloses a technology for data transmission incorporating a hybrid automatic repeat request (ARQ) function at each node in an ad hoc network (for example, patent literature) 1).

  Further, there is a document that discloses a wired / wireless video communication system in which bit error probability reference values are set to be different from each other for each packet (see, for example, Patent Document 2).

  In addition, there is a document that discloses a technique that makes it possible to accurately grasp a reception situation in data distribution and optimizes the FEC redundancy according to the reception situation (see, for example, Patent Document 3).

  There is also a document that discloses a technique for adapting the amount of redundancy so as to provide a correction capability that allows the maximum allowable packet error rate to be followed (see, for example, Patent Document 4).

Further, there is a document that discloses an ODMRP (On Demand Multicast Routing Protocol) protocol (see, for example, Non-Patent Document 1).
JP 2005-529518 A JP 2001-251279 A JP 2002-330118 A JP-T-2006-505177 SUNG-JU LEE, 2 others, "On-Demand Multicast Routing Protocol in Multihop Wireless Mobile Networks", Mobile Networks and Applications Volume 7, Issue 6 (December 2002), Pages 441-453

  However, since the technique disclosed in Patent Document 1 performs retransmission control of lost packets by ARQ, a certain amount of time is required for a retransmission request and its response. For this reason, in the technique disclosed in Patent Document 1, the time from when multicast data is transmitted to when it is received increases, so the real-time property is impaired. In addition, since the variation in time from transmission to reception increases depending on the presence or absence of retransmission for each packet, a process for eliminating this variation is newly required in the multicast reception application.

  In addition, the technique disclosed in Patent Document 2 does not monitor the packet reception status at the multicast receiver, but only estimates it at the multicast sender. Therefore, the FEC adapted to the packet reception status of the multicast receiver. It is difficult to change the redundancy, and the necessary minimum FEC redundancy cannot be set.

  In addition, the above Patent Documents 3 and 4 disclose a technique for optimizing the FEC redundancy, but based on the packet loss information of a data packet transmitted by multicast communication, the technique according to the packet loss information is used. There is no mention or necessity of setting the redundancy.

  The present invention has been made in view of the above circumstances, and in the multicast transfer of the multi-hop network, which is the above-described problem, the redundancy according to the packet loss information of the data packet is set and the packet loss is recovered. An object of the present invention is to provide a communication device, a communication system, a communication control method, and a communication control program.

  In order to achieve this object, the present invention has the following features.

Moreover, the communication apparatus according to the present invention is
A communication device that performs multi-hop multicast transfer,
Receiving means for receiving data packets by multicast communication;
Creating packet loss information for the data packet received by the receiving means, and transmitting the created packet loss information to the transmitting side that transmitted the data packet;
Have
The transmission means includes
A data packet including the packet loss information is created, and the data packet is an independent control packet different from the multicast communication path control packet, and after transmitting the data packet including the packet loss information, a certain period of time is Control is performed so as not to transmit the next control packet .

Further, the communication system according to the present invention includes:
A communication system having at least a transmission device and a reception device, and performing multi-hop multicast transfer between the transmission device and the reception device,
The transmitter is
Transmitting means for transmitting data packets to the receiving device by multicast communication;
Receiving means for receiving packet loss information of the data packet;
Have
The transmission means includes
Based on the packet loss information, set a redundancy according to the packet loss information, generate a data packet with forward error correction with the set redundancy, and transmit the generated data packet,
The receiving device is:
Receiving means for receiving the data packet;
Creating packet loss information for the data packet received by the receiving means;
Transmitting means for transmitting the created packet loss information to the transmitting device;
Have
The packet loss information is transmitted / received as a data packet, and the data packet is an independent control packet different from the multicast communication path control packet. It is characterized by controlling not to transmit .

Further, the communication control method according to the present invention includes:
A communication control method performed by a communication device that performs multi-hop multicast transfer,
A transmission step of transmitting data packets by multicast communication;
The communication device performs a receiving step of receiving packet loss information of the data packet,
The transmission step includes
Based on the packet loss information, set a redundancy according to the packet loss information, generate a data packet with forward error correction with the set redundancy, and transmit the generated data packet ,
The packet loss information is received as a data packet, and the data packet is an independent control packet that is different from the multicast communication path control packet. It is characterized by controlling not to transmit .

Further, the communication control method according to the present invention includes:
A communication control method performed by a communication device that performs multi-hop multicast transfer,
A receiving step of receiving data packets by multicast communication;
Create packet loss information for the data packet received by the receiving step,
The communication device performs a transmission step of transmitting the created packet loss information ,
The packet loss information is transmitted as a data packet, and the data packet is an independent control packet that is different from the multicast communication path control packet. It is characterized by controlling not to transmit .

Further, the communication control method according to the present invention includes:
A communication control method that is performed in a communication system that has at least a transmission device and a reception device, and performs multi-hop multicast transfer between the transmission device and the reception device,
A transmitting step in which the transmitting device transmits a data packet to the receiving device by multicast communication;
A receiving step in which the receiving device receives the data packet;
The receiving device creates packet loss information for the data packet received by the receiving step, and transmits the created packet loss information to the transmitting device;
A receiving step in which the transmitting device receives the packet loss information;
Have
The transmission step in the transmission device includes:
Based on the packet loss information, set a redundancy according to the packet loss information, generate a data packet with forward error correction with the set redundancy, and transmit the generated data packet ,
The packet loss information is transmitted / received as a data packet, and the data packet is an independent control packet different from the multicast communication path control packet. It is characterized by controlling not to transmit .

The communication control program according to the present invention is
A communication control program to be executed by a communication device that performs multi-hop multicast transfer,
Transmission processing for transmitting data packets by multicast communication;
Receiving processing to receive packet loss information of the data packet, causing the communication device to execute,
The transmission process includes
Based on the packet loss information, set a redundancy according to the packet loss information, generate a data packet with forward error correction with the set redundancy, and transmit the generated data packet ,
The packet loss information is received as a data packet, and the data packet is an independent control packet that is different from the multicast communication path control packet. It is characterized by controlling not to transmit .

The communication control program according to the present invention is
A communication control program to be executed by a communication device that performs multi-hop multicast transfer,
A reception process for receiving data packets by multicast communication;
Create packet loss information for the data packet received by the reception process,
Transmitting the created packet loss information to the communication device, and
The packet loss information is transmitted as a data packet, and the data packet is an independent control packet that is different from the multicast communication path control packet. It is characterized by controlling not to transmit .

  According to the present invention, it is possible to set the redundancy according to the packet loss information of the data packet and recover the packet loss in the multicast transfer of the multi-hop network.

<Features of communication system>
First, the features of the communication system in the present embodiment will be described with reference to FIG.

  The communication system in the present embodiment includes at least a transmission device (communication terminal: equivalent to S) and a reception device (communication terminal: equivalent to R1, R2), and the transmission device (S) and the reception device (R1, It is a communication system that performs multi-hop multicast transfer with R2).

  Then, the transmitting device (S) transmits the data packet to the receiving devices (R1, R2) by multicast communication.

  The receiving device (R1, R2) creates packet loss information for the data packet received by the receiving device (R1, R2) itself, and transmits the created packet loss information to the transmitting device (S).

  The transmitting device (S) receives the packet loss information transmitted by the receiving device (R1, R2), sets the redundancy according to the received packet loss information based on the received packet loss information, and A data packet in which forward error correction is performed with the set redundancy is generated, and the generated data packet is transmitted.

  Thereby, in the multicast transfer of the multihop network, it is possible to set the redundancy according to the packet loss information of the data packet and recover the packet loss. Hereinafter, a communication system according to the present embodiment will be described in detail with reference to the accompanying drawings.

(First embodiment)
<System configuration of communication system>
First, a communication system in the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a system configuration of a communication system according to the present embodiment, and shows an arrangement of communication terminals in a wireless multi-hop network.

  In the communication system in the present embodiment, as shown in FIG. 1, communication terminals (S, R1, R2, N1, N2, N3, N4, N5, N6, N7) constitute a wireless multi-hop network.

  Note that the radio wave reach distance of each communication terminal (S, R1, R2, N1, N2, N3, N4, N5, N6, N7) is an area indicated by a circle surrounding each communication terminal as shown in FIG. . And the communication terminals in the radio wave reachable distance communicate with each other.

  The communication terminals (S, R1, R2, N1, N2, N3, N4, N5, N6, N7) in the present embodiment start the multicast routing protocol ODMRP (On Demand Multicast Routing Protocol), Multicast data is transferred.

  In FIG. 1, when the communication terminal (S) is a multicast transmission terminal (S) and the communication terminals (R1, R2) are multicast reception terminals (R1, R2), the transmission terminal (S) transmits. The multicast data to be transferred is transferred in the order of N1 → N2 → N3, the multicast data transferred by the communication terminal (N3) is transferred by the communication terminal (N4), and the multicast data transferred by the communication terminal (N4) is received by the receiving terminal. (R1) will receive.

  Further, the multicast data transferred by the communication terminal (N3) is transferred by the communication terminal (N5), and the multicast data transferred by the communication terminal (N5) is received by the receiving terminal (R2).

  The communication system in the present embodiment can apply, for example, the ODMRP (On Demand Multicast Routing Protocol) protocol disclosed in Non-Patent Document 1 as a multicast routing protocol on the wireless multi-hop network. is there.

  As a moving image compression method, for example, a well-known MPEG4 Visual, ISO / IEC 14496-2 technique can be applied.

<Internal configuration of communication terminal>
Next, the internal configuration of the communication terminal constituting the communication system shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a detailed diagram showing the internal configuration of the communication terminals (S, R1, R2, N1, N2, N3, N4, N5, N6, N7) of the present embodiment. In addition, since the internal configuration of each communication terminal (S, R1, R2, N1, N2, N3, N4, N5, N6, N7) will be configured in the same way, in the following description, the communication terminal (S) will be described. explain.

  As shown in FIG. 2, the communication terminal (S) of this embodiment includes an antenna (N11), a radio processing unit (N12), a path control unit (N13), a message cache (N14), and a tree management unit. (N15), member management unit (N16), communication buffer (N17), application processing unit (N18), FEC encoding unit (N19), buffer (N20), and FEC redundancy control unit (N21) And an FEC decoding unit (N22) and a buffer (N23).

  The antenna (N11) transmits and receives radio waves.

  The wireless processing unit (N12) performs data communication of the wireless network.

  The route control unit (N13) creates, changes, and deletes a route for performing multi-hop data transfer.

  The message cache (N14) retains data received once and is used for confirming the identity of data received again later.

  The tree management unit (N15) manages a tree structure including peripheral communication terminals in order to construct a route of the communication terminal itself (S).

  The member management unit (N16) manages information on the multicast group to which the communication terminal itself (S) belongs.

  The application processing unit (N18) transmits and receives application data such as audio and video.

  The communication buffer (N17) temporarily holds application data.

  The FEC encoding unit (N19) generates an FEC redundant packet from the application data packet.

  The buffer (N20) is a buffer of the FEC encoding unit (N19).

  The FEC redundancy control unit (N21) determines the redundancy at the time of FEC encoding.

  The FEC decoding unit (N22) restores the application data packet received from the network and the packet lost from the FEC redundant packet.

  The buffer (N23) is a buffer of the FEC decoding unit (N22).

<Control action>
Next, the control operation in the communication system of the present embodiment will be described. In the following description, the method of the present embodiment and a related method for comparison with the method of the present embodiment will be described.

  FIG. 3 shows path construction for transferring multicast data. In FIG. 3, the multicast communication path control packet JoinQuery is abbreviated as “JQ”, and JoinReply is abbreviated as “JR”.

(Path construction of related methods)
First, the path construction of the related technique will be described with reference to FIG. In the following description, the route construction of S → N1 → N2 → N3 → N4 → R1 will be described, but the route construction of S → N1 → N2 → N3 → N5 → R2 is similarly performed.

  In FIG. 3, the communication terminal (S) is a transmission terminal (S), and the communication terminal (R1) is a reception terminal (R1). Further, the communication terminals (N1, N2, N3, N4) existing between the transmitting terminal (S) and the receiving terminal (R1) are relay terminals (N1, N2, N3, N4).

  After the transmission data (S1) of the multicast group (G1) is generated at the transmission terminal (S), the transmission terminal (S) transmits a JoinQuery packet JQ11 for searching for the reception terminal (R1).

  This JoinQuery packet JQ11 is transferred in the order of JQ12 → JQ13 → JQ14 → JQ15 by relay terminals (N1, N2, N3, N4) existing in the network. As a result, all the terminals (N1, N2, N3, N4, R1) receive the JoinQuery packet.

  The receiving terminal (R1) that is a member of the multicast group (G1) of the transmission data (S1) creates a JoinReply packet JR11 including the upstream neighboring terminal information N4. The upstream adjacent terminal information N4 is information for identifying the communication terminal (N4) adjacent upstream of the receiving terminal (R1).

  The receiving terminal (R1) transmits the JoinReply packet JR11 including the upstream adjacent terminal information N4 in the direction opposite to the path along which the JoinQuery packet has been transferred, and requests to join the multicast group (G1).

  The JoinReply packet JR11 transmitted by the receiving terminal (R1) is transferred from the relay terminal (N4, N3, N2, N1) in the network as JR12 → JR13 → JR14 → JR15, and delivered to the transmitting terminal (S). The transmitting terminal (S) recognizes the presence of the receiving terminal (R1). Thereby, a route from the transmission terminal (S) to the reception terminal (R1) is established.

  Then, the multicast data packet transmitted by the transmitting terminal (S) is multi-hop transferred by the relay terminals (N1, N2, N3, N4) on the constructed path, and is received by the receiving terminal (R1). .

(Route construction of the method of this embodiment)
Next, referring to FIG. 3, the path construction of the method of this embodiment will be described. In the following description, the route construction of S → N1 → N2 → N3 → N4 → R1 will be described, but the route construction of S → N1 → N2 → N3 → N5 → R2 is similarly performed.

  The route construction of the method of the present embodiment is the same route construction as the related method.

  However, the route construction of the method of the present embodiment is that the JoinReply packet JR11 transmitted by the receiving terminal (R1) that is a member of the multicast group (G1) is a packet that uses FEC to determine whether or not a multicast data packet has been received. Packet statistical information such as whether or not restoration is possible is included.

<Route control processing>
Next, the route control process of the communication terminal will be described with reference to FIG. Note that a sequence number described later is a numerical value held by one in one communication terminal, and is a numerical value that increases by one each time a JoinQuery packet is transmitted.

(JoinQuery processing of related methods)
When the transmission data (S1) of the multicast group (G1) is generated in the application processing unit (N18) of the sending terminal (S), the JoinQuery processing of the related technique creates a JoinQuery packet in the routing control unit (N13) The created JoinQuery packet is transmitted via the wireless processing unit (N12) and the antenna (N11).

  In the communication terminal that has received the JoinQuery packet, the path control unit (N13) receives the JoinQuery packet via the antenna (N11) and the wireless processing unit (N12).

  The path control unit (N13) refers to the message cache (N14) using the transmission terminal address included in the JoinQuery packet and the transmission terminal sequence number as keys, and determines whether or not it is a JoinQuery packet received for the first time.

  In the case of a JoinQuery packet received for the first time, the route control unit (N13) adds 1 to the hop count in the JoinQuery packet and transmits it to another communication terminal.

  In addition, when the communication terminal itself is a member of the multicast group (G1), the route control unit (N13), in the member management unit (N16), the address of the participating multicast group (G1), the last JoinQuery reception time, Manages JoinQuery sending terminals and performs JoinReply sending processing.

  Note that the sending terminal (S), which is the multicast sender, does not send the JoinQuery for a certain period after sending the JoinQuery, even if multicast data occurs, and creates the JoinQuery again when the certain period has passed. And send the created JoinQuery.

(JoinReply processing of related methods)
The JoinReply process of the related method specifies an upstream adjacent terminal (equivalent to the immediately preceding JoinQuery transmission terminal) in the route control unit (N13) of the communication terminal, creates a JoinReply packet, and creates the JoinReply packet as a wireless processing unit (N12). ) And the antenna (N11).

  When a communication terminal that has received a JoinReply packet has been designated as an upstream adjacent terminal of the JoinReply packet, the tree management unit (N15) indicates that the receiver of the multicast group (G1) exists downstream. Manage and send JoinReply packets to upstream neighbors.

(JoinQuery processing in the method of this embodiment)
The JoinQuery process in the method of the present embodiment is performed in the same manner as the JoinQuery process in the related method.

(JoinReply process in the method of this embodiment)
In the JoinReply process in the method of the present embodiment, the JoinReply packet in the JoinReply process in the related method is changed to a JoinReply packet corresponding to FEC.

  Note that the FEC-compatible JoinReply packet includes packet statistical information in the field of the JoinReply packet of the related technique.

  Further, the FEC-supported JoinReply packet is transferred in a multihop manner to the transmission terminal (S), which is a multicast sender, in the same manner as the JoinReply packet of the related technique.

<Packet statistical information generation processing>
Next, packet statistical information generation processing, which is a feature of this embodiment, will be described.

  First, when receiving a multicast data packet, the receiving terminal (R1) stores a packet log using the sequence number as a key.

  The packet log includes reception status information of each data packet, FEC restoration status information, and packet statistics information for a past certain period.

  The reception status information of each data packet is information for specifying whether or not each data packet has been received.

  The FEC restoration status information is information for specifying whether or not packet restoration has been performed using FEC for a data packet in which packet loss has occurred.

  The packet statistical information for the past certain period is statistical information regarding the data packet received by the receiving terminal (R1) within the past certain period. Packet statistics include information such as the number of packet losses in the past fixed period, the number of packet restorations by FEC, the number of consecutive packet losses, the number of packet losses in the FEC block, and the number of hops on the route from the multicast sender to the receiver. Can be mentioned.

<Multicast data processing>
Next, multicast data processing will be described with reference to FIG.

(Multicast data processing of related methods)
In the multicast data processing of the related method, when transmission data (S1) of the multicast group (G1) is generated in the application processing unit (N18) of the transmission terminal (S), the packet is temporarily stored in the communication buffer (N17). After adding the sequence number, transmission is performed via the wireless processing unit (N12) and the antenna (N11) according to the route of the route control unit (N13).

  The communication terminal (N1, N2, N3, N4, R1) that received the multicast data packet receives the multicast data packet through the antenna (N11) and the wireless processing unit (N12). .

  For communication terminals (N1, N2, N3, N4) where the receiver of the multicast group (G1) exists downstream, refer to the message cache (N14) using the transmission terminal address and the transmission terminal sequence number as keys. It is determined whether the packet is received for the first time.

  If the packet is received for the first time, it is transmitted to another communication terminal. If the packet is not received for the first time, nothing is done.

  In addition, nothing is done in a communication terminal in which no receiver of the multicast group (G1) exists downstream.

  Further, in the communication terminal (N1, N2, N3, N4, R1) that has received the multicast data packet, if the communication terminal itself is a member of the multicast group (G1), the packet is temporarily stored in the communication buffer ( N17), and by referring to the message cache (N14) using the transmission terminal address and the transmission terminal sequence number as keys, it is determined whether or not the packet is received for the first time.

  If the packet is received for the first time, it is transmitted to the application processing unit (N18). If the packet is not received for the first time, nothing is done.

(Multicast data processing in the method of this embodiment)
The multicast data processing in the method of the present embodiment performs FEC encoding processing of multicast data packets at the time of multicast data transmission. Further, when multicast data is received, FEC decoding processing of the multicast data packet is performed.

(FEC encoding process at the time of multicast data transmission in the method of this embodiment)
First, FEC encoding processing at the time of multicast data transmission in the method of the present embodiment will be described.

  In the multicast data transmission process according to the method of the present embodiment, the multicast data packet is stored in the communication buffer (N17), the sequence number is added, and then the FEC encoding process is performed. Hereinafter, the FEC encoding process will be described in detail with reference to FIG.

  First, FEC redundancy: M is determined from the packet type by the FEC redundancy determination method described later (step S402).

  Next, it is determined whether or not the determined FEC redundancy: M is changed (step S403). If the FEC redundancy: M determined in step S403 is different from the immediately preceding FEC redundancy, the FEC redundancy is determined. : It is determined that there is a change in M (step S403 / present), and the FEC encoding process is performed (step S404).

  Next, the multicast data packet stored in the communication buffer (N17) is stored in the buffer (N20) of the FEC encoding unit (N19) (step S405).

  If the FEC redundancy: M determined in step S403 is the same as the previous FEC redundancy, it is determined that the FEC redundancy: M has not been changed (step S403 / no), and the FEC encoding process is performed. First, the multicast data packet is stored in the buffer (N20) of the FEC encoding unit (N19) (step S405).

  Next, it is determined whether or not the number of packets stored in the buffer (N20) has become FEC redundancy: M or more (step S406), and the number of packets stored in the buffer (N20) is FEC redundancy: M or more. If it is determined (step S406 / Yes), the FEC operation is performed on the packet group (hereinafter referred to as “FEC block”) in the buffer (N20), and an FEC redundant packet (hereinafter, “ FEC packet ”is generated (step S407), transmitted via the wireless processing unit (N12) and the antenna (N11), and the process is terminated (step S408).

  If it is determined that the number of packets stored in the buffer (N20) is less than FEC redundancy: M (step S406 / No), the process ends (step S408).

  The transmission timing of the FEC packet is not particularly limited. The FEC encoding unit (N19) can be configured to transmit immediately after copying the FEC packet, or transmitted at the same timing as the subsequent FEC packet. It is possible to construct as follows.

  In transmitting the FEC packet, it is preferable to transmit at an appropriate packet interval in consideration of performing multi-hop transfer in the downstream communication terminal. For example, as the packet interval, it is preferable that the transmission rate is 1/3 or less of the wireless transmission rate.

  In this way, by setting the transmission rate and transmitting the FEC packet at the set transmission rate, it becomes possible to control to secure the transfer time when performing multi-hop transfer in the downstream communication terminal. .

<Configuration of FEC packet>
Next, the contents of the FEC packet and the method for generating the FEC packet will be described with reference to FIG. FIG. 5 shows the FEC packet field.

  As shown in FIG. 5, the FEC packet is composed of “NumOfPackets”, “Starting Sequence Number”, “Length Recovery”, and “FEC payload”.

  “NumOfPackets” is the number of packets in the FEC block.

  “Starting Sequence Number” is the sequence number of the first packet in the FEC block.

  “Length Recovery” is information calculated from the packet length of the multicast data packet.

  “FEC payload” is FEC redundancy information calculated from each packet of the FEC block.

<FEC redundancy determination method>
Next, the FEC redundancy determination method will be described.

  The FEC redundancy determination method has two steps, a step performed before multicast data transfer and a step performed during multicast data transfer.

<Stage to perform before multicast data transfer>
First, steps performed before multicast data transfer will be described with reference to FIG. FIG. 6 shows an example of the relationship between the pre-FEC packet loss rate (pre-FEC loss rate) Lb and the post-FEC packet loss rate (post-FEC loss rate) La when the FEC redundancy is M. It is a graph.

  First, the relationship between the FEC redundancy: M, the pre-FEC loss rate Lb, and the post-FEC loss rate La will be described.

  When the packet loss is random, the pre-FEC loss rate Lb and the post-FEC loss rate La have the relationship shown in FIG.

  For example, when the pre-FEC loss rate Lb = 10%, and the FEC redundancy is M = 10, the post-FEC loss rate La = about 6.5%. According to this, when the target value of the post-FEC loss rate La is set, the optimum value of FEC redundancy: M is obtained with respect to the pre-FEC loss rate Lb. A simple example is shown below.

  The pre-FEC loss rate Lb is regarded as a function of the post-FEC loss rate La, and can be approximated by the following (Equation 1) using an appropriate parameter a.

(Lb) = a × (La) ² ... (Formula 1)

  FEC redundancy: The relationship between M and parameter a is obtained as shown in Table 1. The numerical values shown in Table 1 are examples.

  From Table 1, the relationship between FEC redundancy: M and parameter a is approximated as in the following (Equation 2).

^{M = 0.22954 × a 2 - 0.40831} × a + 0.2834 ··· ( Equation 2)

  In addition, using the relationship described above, when the pre-FEC loss rate Lb and the post-FEC loss rate target value Lt are given, the optimal FEC redundancy: M ′ is obtained by the following (Equation 3).

M '= 0.22954 × ((Lb ) / (La) 2) 2 - 0.40831 × ((Lb) / (La) 2) + 0.2834 ··· ( Equation 3)

  Next, the post-FEC loss rate target value Lt will be described with reference to FIG. FIG. 7 is a graph showing an example of the relationship between the post-FEC loss rate La and the pre-FEC loss rate Lb.

  The post-FEC loss rate target value Lt is set under the following conditions according to the pre-FEC loss rate Lb.

When 0% ≤ Lb ≤ 10%, Lt = 2%
When 10% <Lb ≤ 20%, Lt = 5%
When 20% <Lb, Lt = La

  However, the range of the pre-FEC loss rate Lb in each condition and the post-FEC loss rate target value Lt are examples, and are not limited to the above-described conditions, and any condition can be set as appropriate. .

<Stage to be performed during multicast data transfer>
Next, steps performed during multicast data transfer will be described.

  The multicast transmission terminal (S) receives a JoinReply packet including packet statistical information. Note that a JoinReply packet including packet statistical information is generated at the multicast receiving terminal (R1).

  When the multicast transmission terminal (S) receives a JoinReply packet including packet statistical information, the multicast transmission terminal (S) sets an appropriate FEC redundancy: M ′ to restore the pre-FEC loss rate Lb to the post-FEC loss rate target value Lt. The current FEC redundancy: M difference: ΔM is calculated.

  Next, the randomness of the packet loss is confirmed based on the number of consecutive packet losses in the packet statistical information and the number of packet losses in the FEC block.

  If it is determined that the randomness of the packet loss is high, ΔM obtained as described above is reduced or set to 0 and added to the current FEC redundancy: M to obtain an appropriate FEC redundancy: M ′. Obtained by the following (Equation 4).

  M ′ = M + ΔM (Formula 4)

  Next, a new FEC redundancy: Mn is determined by the following (Expression 5) using the smoothing factor α (0 ≦ α <1).

  Mn = (α × M) + ((1-α) × M ′) (Formula 5)

  In addition, as a method for confirming the randomness of packet loss, for example, the following method can be cited.

  Packet randomness is high when the number of consecutive packet losses is larger than a predetermined value, or when the ratio of the number of packet losses in the FEC block is 2 or more is larger than a predetermined value. Judge.

  In this way, based on continuous information (number of continuous packet loss, number of packet loss in FEC block) to identify whether packet loss of data packet occurs continuously or randomly, data packet It is possible to avoid occurrence of packet loss by determining whether the packet loss is continuously generated or randomly generated, and changing the FEC redundancy according to the determination result.

  When there are a plurality of multicast receiving terminals (R1, R2), packet statistical information generated at each multicast receiving terminal (R1, R2) is notified to the multicast transmitting terminal (S).

  In this case, the above-described (Equation 4) and (Equation 5) are calculated for each packet statistical information generated at each multicast receiving terminal (R1, R2), and Mn for each packet statistical information is calculated. . A value obtained by comprehensively evaluating a plurality of Mn values for each packet statistical information is defined as Mn.

  However, as a comprehensive evaluation method, for example, a method of taking an average value of a plurality of Mn values, a method of taking a median value of a plurality of Mn values, a method of taking a maximum value of a plurality of Mn values, a plurality of methods And a method of taking the minimum value of Mn.

  It is also possible to control to change the FEC redundancy according to the number of hops in the route from the multicast sender to the receiver. For example, if the number of hops is large, the distance from the sender to the receiver becomes long, and therefore the occurrence of packet loss increases. For this reason, when the number of hops is large, control is performed to increase the FEC redundancy. Conversely, if the number of hops is small, the distance from the sender to the receiver is shortened, so that the occurrence of packet loss is reduced. For this reason, when the number of hops is small, the FEC redundancy is controlled to be low. In this way, it is possible to avoid the occurrence of packet loss by controlling the FEC redundancy to be changed according to the number of hops in the route from the multicast sender to the receiver.

<Method for determining FEC redundancy for I-frames in video>
Further, when the multicast data is a moving image, the following method is applied to suppress the packet loss of the I frame more than other frames (hereinafter, non-I frames).

  First, two FEC redundancy levels (M1, M2) are managed (where M1 <M2), FEC redundancy is M1 for non-I frames, and FEC encoding is M2 for I frames. I do.

  Thus, when a plurality of FEC redundancy levels are managed and the multicast data is a moving image, it is preferable to perform FEC encoding with a high FEC redundancy for the I frame of the moving image.

  In addition, when the frame type changes, FEC encoding is performed even when the number of packets in the buffer (N20) of the FEC encoding unit (N19) is less than a predetermined number, and packets of a plurality of video frames are the same. Control so as not to enter the FEC block.

  In the above method, multiple FEC redundancy levels are managed, and when multicast data is a moving image, FEC encoding is performed with high FEC redundancy for the I frame of the moving image. In the case where priority is given to the data packet to be processed, it is possible to perform FEC encoding with redundancy according to the priority.

  For example, if three FEC redundancy levels (M1, M2, M3) are managed (where M1 <M2 <M3) and the priority given to the data packet transmitted by multicast communication is high, the FEC redundancy level : When FEC encoding is performed with M3 and the priority given to a data packet transmitted by multicast communication is low, control can be performed so that FEC redundancy is performed with FEC redundancy: M1.

(FEC decoding process when receiving multicast data in the method of this embodiment)
Next, FEC decoding processing at the time of multicast data reception in the method of the present embodiment will be described.

  In the multicast data processing in the present embodiment, the FEC decoding processing is performed when the multicast data packet is stored in the communication buffer (N17). Hereinafter, the FEC decoding process and the FEC decoding restoration process will be described with reference to FIGS. FIG. 8 shows the FEC decoding process, and FIG. 9 shows the FEC decoding restoration process.

(FEC decoding process)
First, the received multicast data packets are stored in the buffer (N20) of the FEC decoding unit (N19), and are arranged in the sequence number order (step S802).

  Next, it is identified whether the packet is a multicast data packet or an FEC packet (step S803).

  If it is an FEC packet (step S803 / FEC packet), the FECDEC-delay timer is started (step S804), and the process is terminated (step S805).

  If it is a multicast data packet (step S803 / non-FEC packet), the FECDEC-delay timer is not started and the process is terminated (step S805).

  In step S804, the FECDEC-delay timer is started, and when the FECDEC timer is exceeded, FEC decoding restoration processing is started (FIG. 9: step S901). The reason why the FEC decoding process is not performed immediately after receiving the FEC packet is that the order of the data packet and the FEC packet in the FEC block may be reversed during network transfer. This is because it is necessary to wait for the data packet of the FEC block after receiving the FEC packet in order to receive the data packet of the FEC block.

(FEC decoding restoration process)
In the FEC decoding restoration process, as shown in FIG. 9, the sequence number of the data packet in the FEC block is obtained from the “NumOfPackets” field and the “Starting Sequence Number” field of the FEC packet (step S902).

  Next, FEC restoration calculation processing is performed using the FEC block and the FEC packet (step S903).

  In the FEC restoration calculation process, lost packets are restored from each packet in the FEC block and “payload” of the FEC packet.

  Further, the packet length of the lost packet is restored from the length of each packet in the FEC block and “Length Recovery” of the FEC packet.

  Next, the FEC restored packets are stored in the buffer (N23) of the FEC decoding unit (N22), and are arranged in order of the sequence number (step S904).

  Next, in the buffer (N23) of the FEC decoding unit (N22), a data packet older than the FEC packet is transmitted to the application processing unit (N18) (step S905), and the process ends (step S906).

  As described above, in the communication system of this embodiment, the multicast transmission terminal (S) acquires the JoinReply packet including the packet statistical information created in the multicast reception terminal (R1, R2). Then, the multicast transmission terminal (S) sets the FEC redundancy according to the number of packet losses in the packet statistical information based on the packet statistical information included in the acquired JoinReply packet, and uses the set FEC redundancy. FEC redundant packet will be generated.

  As a result, the FEC redundancy is set according to the number of packet loss of the data packet that fluctuates depending on the time, location, and network configuration, and the FEC redundancy packet is generated with the set FEC redundancy. It becomes possible to perform recovery.

  If the multicast data is a moving picture, a higher FEC redundancy than other frames (P frame, B frame) is set for the multicast data packet including the I frame of the moving picture, and the set FEC redundancy is set. It is possible to improve the quality of moving images by generating FEC redundant packets at a certain degree.

  Further, by providing an appropriate packet transmission interval when continuously transmitting data packets, it is possible to reduce packet loss that occurs due to the “hidden terminal problem”.

(Second embodiment)
Next, a second embodiment will be described.

  In the first embodiment, packet statistical information generated in multicast receiving terminals (R1, R2) is included in a JoinReply packet and transmitted.

  The second embodiment is characterized in that the packet statistical information generated in the multicast receiving terminals (R1, R2) is not included in the JoinReply packet as in the first embodiment, but is transmitted as an independent control packet. And

  Thereby, the packet statistical information generated in the multicast receiving terminals (R1, R2) can be transmitted to the multicast transmitting terminal (S) using a routing protocol other than ODMRP. Hereinafter, the second embodiment will be described in detail.

  When the multicast receiving terminals (R1, R2) in the second embodiment generate packet statistical information by the same packet statistical information generation processing as in the first embodiment, the generated packet statistical information is independent. As a control packet.

  Note that the packet statistical information generation processing generates packet statistical information using information collected at a predetermined time, or generates packet statistical information using a predetermined number of information. It is possible to do so.

  In addition, after transmitting a control packet including packet statistical information, control is performed so as not to transmit the next control packet for a certain period, and when the certain period elapses, the control packet including packet statistical information again. It is preferable to control to transmit.

  The multicast transmission terminal (S) performs the same multicast data processing as in the first embodiment when receiving a control packet including packet statistical information.

  Thus, the packet statistical information generated in the multicast receiving terminals (R1, R2) is not included in the JoinReply packet as in the first embodiment, but is transmitted as an independent control packet.

  Thereby, the packet statistical information generated in the multicast receiving terminals (R1, R2) can be transmitted to the multicast transmitting terminal (S) using a routing protocol other than ODMRP.

  The above-described embodiments are preferred embodiments of the present invention, and are not intended to limit the scope of the present invention only to the above-described embodiments. It is possible to construct a form with various changes by making corrections and substitutions.

  For example, although the above-described embodiment has been described based on a communication system that performs wireless communication, the technical idea of the present embodiment is not limited to wireless, but can also be applied to wired communication.

  Further, the packet statistical information described above can be configured to be transmitted as a plurality of packet data instead of being transmitted as a single packet data.

  Further, the control operation in the communication terminal constituting the communication system in the above-described embodiment can be executed by hardware, software, or a combined configuration of both.

  In addition, when executing processing using software, a program in which a processing sequence is recorded can be installed in a memory in a computer incorporated in dedicated hardware and executed, or various types of processing can be executed. The program can be installed and executed on a general purpose computer.

  For example, the program can be recorded in advance on a hard disk or a ROM (Read Only Memory) as a recording medium. Alternatively, the program is temporarily stored on a removable recording medium such as a floppy (registered trademark) disk, a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto optical) disk, a DVD (Digital Versatile Disc), a magnetic disk, or a semiconductor memory. Or can be stored (recorded) permanently. Such a removable recording medium can be provided as so-called package software.

  The program is installed on the computer from the removable recording medium as described above, or is wirelessly transferred from the download site to the computer, or is wired to the computer via a network such as a LAN (Local Area Network) or the Internet. On the other hand, the computer can receive the transferred program and install it on a recording medium such as a built-in hard disk.

  In addition to being executed in time series in accordance with the processing operations described in the above embodiments, the processing capability of the apparatus that executes the processing, or to be executed in parallel or individually as required Is also possible.

  As is apparent from the above description, the present embodiment is characterized by having the following configuration.

The communication apparatus according to the present embodiment is
A communication device that performs multi-hop multicast transfer,
Transmission means for transmitting data packets by multicast communication;
Receiving means for receiving packet loss information of the data packet;
Have
The transmission means includes
Based on the packet loss information, setting a redundancy according to the packet loss information, generating a data packet with forward error correction with the set redundancy, and transmitting the generated data packet Features.

In the communication apparatus according to the present embodiment,
The packet loss information is
It is information of packet loss on the receiving side that has received the data packet.

In the communication apparatus according to the present embodiment,
The receiving means includes
When there are a plurality of receiving sides, the packet loss information is received from each receiving side,
The transmission means includes
On the basis of the packet loss information received from each receiving side, a redundancy according to the packet loss information is set.

In the communication apparatus according to the present embodiment,
The receiving means includes
Receiving continuous information for identifying whether packet loss of the data packet occurs continuously or randomly;
The transmission means includes
Based on the continuous information, it is determined whether packet loss of the data packet occurs continuously or randomly, and the redundancy is changed according to the determination result.

In the communication apparatus according to the present embodiment,
The receiving means includes
Receiving the multi-hop number of the data packet;
The transmission means includes
Based on the number of multi-hops, the redundancy according to the number of multi-hops is set.

In the communication apparatus according to the present embodiment,
The transmission means includes
A plurality of redundancy levels are managed, and when a data packet transmitted by multicast communication is a moving image, a high redundancy is set for the I frame of the moving image among the plurality of redundancy levels. .

In the communication apparatus according to the present embodiment,
The transmission means includes
A plurality of redundancy levels are managed, and when a priority is given to a data packet transmitted by multicast communication, a redundancy level corresponding to the priority level is set.

In the communication apparatus according to the present embodiment,
The transmission means includes
A high redundancy is set for data packets with high priority, and a low redundancy is set for data packets with low priority.

In addition, the communication apparatus according to the present embodiment is
It has a setting means which sets the transmission rate of the data packet.

In the communication apparatus according to the present embodiment,
The receiving means includes
A data packet including the packet loss information is received, and the data packet is a multicast communication path control packet.

In the communication apparatus according to the present embodiment,
The receiving means includes
A data packet including the packet loss information is received, and the data packet is an independent control packet different from a multicast communication path control packet.

In the communication apparatus according to the present embodiment,
The receiving means includes
A data packet including the packet loss information, the continuous information, and the multihop number is received.

In addition, the communication apparatus according to the present embodiment is
A communication device that performs multi-hop multicast transfer,
Receiving means for receiving data packets by multicast communication;
Creating packet loss information for the data packet received by the receiving means, and transmitting the created packet loss information to the transmitting side that transmitted the data packet;
It is characterized by having.

In the communication apparatus according to the present embodiment,
The transmission means includes
It is characterized in that continuous information for specifying whether packet loss of the data packet is continuously generated or randomly generated is created, and the created continuous information is transmitted to the transmission side.

In the communication apparatus according to the present embodiment,
The transmission means includes
The multi-hop number of the data packet is transmitted to the transmission side.

In the communication apparatus according to the present embodiment,
The transmission means includes
A data packet including the packet loss information is created, and the data packet is a multicast communication path control packet.

In the communication apparatus according to the present embodiment,
The transmission means includes
A data packet including the packet loss information is created, and the data packet is an independent control packet different from the multicast communication path control packet.

In the communication apparatus according to the present embodiment,
The transmission means includes
A data packet including the packet loss information, the continuous information, and the multihop number is created.

In addition, the communication system according to the present embodiment is
A communication system having at least a transmission device and a reception device, and performing multi-hop multicast transfer between the transmission device and the reception device,
The transmitter is
Transmitting means for transmitting data packets to the receiving device by multicast communication;
Receiving means for receiving packet loss information of the data packet;
Have
The transmission means includes
Based on the packet loss information, set a redundancy according to the packet loss information, generate a data packet with forward error correction with the set redundancy, and transmit the generated data packet,
The receiving device is:
Receiving means for receiving the data packet;
Creating packet loss information for the data packet received by the receiving means, and transmitting the created packet loss information to the transmitting device;
It is characterized by having.

The communication control method according to the present embodiment is as follows:
A communication control method performed by a communication device that performs multi-hop multicast transfer,
A transmission step of transmitting data packets by multicast communication;
The communication device performs a receiving step of receiving packet loss information of the data packet,
The transmission step includes
Based on the packet loss information, setting a redundancy according to the packet loss information, generating a data packet with forward error correction with the set redundancy, and transmitting the generated data packet Features.

The communication control method according to the present embodiment is as follows:
A communication control method performed by a communication device that performs multi-hop multicast transfer,
A receiving step of receiving data packets by multicast communication;
The communication apparatus performs a transmission step of creating packet loss information for the data packet received by the reception step and transmitting the created packet loss information.

The communication control method according to the present embodiment is as follows:
A communication control method that is performed in a communication system that has at least a transmission device and a reception device, and performs multi-hop multicast transfer between the transmission device and the reception device,
A transmitting step in which the transmitting device transmits a data packet to the receiving device by multicast communication;
A receiving step in which the receiving device receives the data packet;
The receiving device creates packet loss information for the data packet received by the receiving step, and transmits the created packet loss information to the transmitting device;
A receiving step in which the transmitting device receives the packet loss information;
Have
The transmission step in the transmission device includes:
Based on the packet loss information, setting a redundancy according to the packet loss information, generating a data packet with forward error correction with the set redundancy, and transmitting the generated data packet Features.

The communication control program according to the present embodiment is
A communication control program to be executed by a communication device that performs multi-hop multicast transfer,
Transmission processing for transmitting data packets by multicast communication;
Receiving processing to receive packet loss information of the data packet, causing the communication device to execute,
The transmission process includes
Based on the packet loss information, setting a redundancy according to the packet loss information, generating a data packet with forward error correction with the set redundancy, and transmitting the generated data packet Features.

The communication control program according to the present embodiment is
A communication control program to be executed by a communication device that performs multi-hop multicast transfer,
A reception process for receiving data packets by multicast communication;
A packet loss information for the data packet received by the reception process is created, and a transmission process for transmitting the created packet loss information is executed by the communication device.

  A communication device, a communication system, a communication control method, and a communication control program according to the present invention are used for multicast communication over a multi-hop network, for example, multimedia communication services such as video distribution, audio distribution, and other types of information distribution. Applicable.

It is a figure which shows the system configuration | structure of the communication system of a present Example. It is a figure which shows the internal structure of the communication terminal which comprises the communication system of a present Example. It is a figure for demonstrating the path | route construction which forwards multicast data. It is a figure for demonstrating a FEC encoding process. It is a figure which shows a FEC packet field. It is a graph which shows an example of the relationship between the packet loss rate before FEC restoration (loss rate before FEC) Lb in case of FEC redundancy: M, and the packet loss rate after FEC restoration (loss rate after FEC) La. It is a graph which shows an example of the relationship between the loss rate La after FEC and the loss rate Lb before FEC. It is a figure for demonstrating a FEC decoding process. It is a figure for demonstrating a FEC decoding decompression | restoration process.

Explanation of symbols

S, R1, R2, N1, N2, N3, N4, N5, N6, N7 Communication terminal
N11 antenna
N12 wireless processor
N13 route controller
N14 message cache
N15 Tree Management Department
N16 Member Management Department
N17 communication buffer
N18 application processor
N19 FEC encoding part
N20 buffer
N21 FEC redundancy controller
N22 FEC decoding unit
N23 buffer

Claims (4)

A communication system having at least a transmission device and a reception device, and performing multi-hop multicast transfer between the transmission device and the reception device,
The transmitter is
First transmission means for performing forward error correction on a first data packet received by multicast communication and transmitting the first data packet as a second data packet to the receiving device;
First receiving means for receiving a third data packet including packet loss information in the receiving device of the second data packet;
Have
The receiving device is:
Second receiving means for receiving the second data packet;
The second data packet is restored by forward error correction, the packet loss information including the packet loss rate before the restoration is created, and the third data packet including the packet loss information is transmitted to the transmission device. Second transmitting means for
Have
The first transmission means includes
Forward error using redundancy determined based on the packet loss rate before restoration and the target value of the packet loss rate after restoration by forward error correction in the receiving apparatus determined from the packet loss rate before restoration Making a correction to generate the second data packet, sending the second data packet,
The third data packet is an independent control packet different from the multicast communication path control packet, and the receiving apparatus transmits the next control packet for a certain period after transmitting the third data packet. A communication system characterized by not. A communication control method performed by a communication device that performs multi-hop multicast transfer,
A transmission step of transmitting the received first data packet as a second data packet by multicast communication;
Receiving the packet loss information including a packet loss rate before restoration of the second data packet by forward error correction at the destination of the second data packet as a third data packet; and Performed
The transmission step includes
The redundancy is set based on the packet loss rate before restoration and the target value of the packet loss rate after restoration by forward error correction at the destination determined from the packet loss rate before restoration, and the redundancy To perform forward error correction on the first data packet to generate the second data packet, and to transmit the second data packet to the destination,
The third data packet is an independent control packet different from the multicast communication path control packet, and is controlled so that the next control packet is not transmitted for a certain period after the third data packet is transmitted. The communication control method characterized by the above-mentioned. A communication control method that is performed in a communication system that has at least a transmission device and a reception device, and performs multi-hop multicast transfer between the transmission device and the reception device,
A first transmission step in which the transmitting device performs forward error correction on the first data packet received by multicast communication and transmits the first data packet to the receiving device as a second data packet;
A first receiving step in which the receiving device receives the second data packet;
The receiving device performs restoration by forward error correction on the second data packet received in the first receiving step, creates packet loss information including a packet loss rate before the restoration, and sets the packet loss information to A second transmission step of transmitting a third data packet including to the transmission device;
A second receiving step in which the transmitting device receives the third data packet;
Have
The first transmission step includes
Forward error using redundancy determined based on the packet loss rate before restoration and the target value of the packet loss rate after restoration by forward error correction in the receiving apparatus determined from the packet loss rate before restoration Making a correction to generate the second data packet, sending the second data packet,
The third data packet is an independent control packet different from the multicast communication path control packet, and the second transmission step performs the following control for a certain period of time after transmitting the third data packet. A communication control method characterized by not transmitting a packet. A communication control program to be executed by a communication device that performs multi-hop multicast transfer,
A transmission process for performing a forward error correction on the first data packet received by multicast communication and transmitting it as a second data packet;
A receiving process for receiving a third data packet including packet loss information including a packet loss rate before restoration of the second data packet by forward error correction at a destination of the second data packet; Let the device run,
The transmission process includes
Forward error using redundancy determined based on the packet loss rate before restoration and the target value of the packet loss rate after restoration by forward error correction at the destination determined from the packet loss rate before restoration Making a correction to generate the second data packet, sending the second data packet,
The third data packet is an independent control packet that is different from the multicast communication path control packet, and the third data packet has the following period after the third data packet is transmitted: A communication control program controlled so as not to transmit a control packet.

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